Image forming apparatuses having a recording head to eject droplets such as ink droplets have been used for printers, facsimiles, copiers, and multifunctional machines having a combination of these functions, and specific examples thereof include inkjet recording apparatuses.
Such inkjet recording apparatuses record images by ejecting droplets such as ink droplets from a recording head toward a recording material such as paper sheets, overhead projection (OHP) sheets, and other materials to which an ink can be adhered, to form an ink image on the recording material. Inkjet recording apparatuses are broadly classified into serial inkjet recording apparatuses in which a recording head ejects droplets while moving in a main scanning direction to form an image on a recording material, which is fed in a sub-scanning direction, and line inkjet recording apparatuses which have a fixed line recording head to eject droplets on a recording material fed in a direction perpendicular to the extending direction of the line recording head.
In this application, image forming apparatuses mean apparatuses which eject droplets to adhere the droplets to a recording material such as paper, yarn, fiber, fabric, leather, metal, plastic, glass, wood, and ceramic, thereby forming an image thereon. In addition, image formation means not only formation of a meaningful image such as letters and figures but also formation of a meaningless image such as patterns (i.e., mere adhesion of droplets on a recording material).
Further, ink means not only so-called inks but also other liquids, which can be used for image formation, such as recording liquids, liquid resins, fixing liquids, chemicals and the like liquids.
As mentioned above, the recording material for use in the image forming apparatus of this disclosure is not limited to paper, and other materials to which an ink can be adhered can also be used. In this regard, the recording material is a generic name of a receiving medium, a recording medium, and a recording paper.
In a case in which the liquid-ejecting image forming apparatus is a facility-type inkjet recording apparatus used for recording images in a field such as bookmaking and commercial printing, the inkjet recording apparatus typically has multiple inkjet recording heads, which are thermal inkjet recording heads or piezoelectric inkjet recording heads and each of which is fixedly set so as to extend in a direction perpendicular to the feeding direction of a recording material (without using a carriage), so that images can be formed on the recording material at a high speed only by feeding the recording material.
The inkjet recording apparatus of this kind can produce images at a high speed with low noise. In addition, images can be formed on various kinds of recording materials, and color images can be formed. Therefore, inkjet recording apparatus become widespread.
When a recording material is a fibrous material such as paper, a feathering problem in that a recording ink adhered to the recording material is irregularly penetrated along the fibers of the recording material, thereby forming an image whose outline has feathering, a color bleeding problem in that two adjacent color ink images have an unclear boundary due to mixing of the color inks, a low image density problem, a set off problem in that an ink image is transferred onto a backside of another recording material sheet, an insufficient glossiness problem in that an image having insufficient glossiness is formed, and a fixing problem in that an image having insufficient fixability is formed, can be caused.
In addition, other problems such as primary image quality problems (e.g., a slow drying problem in that a recorded image has a long drying time), and poor image resistance problems (e.g., problems in that resistance of images to water, light, abrasion and ozone is poor) can be caused.
In order to avoid the above-mentioned problems, there are proposals in that a treatment liquid, which can be reacted with the ink used for image formation, is applied to or sprayed on a recording material before or after the image formation operation. In this regard, specific examples of the reaction include absorption of a colorant in the ink, aggregation of a colorant, or the like.
In addition, there is a proposal in that a foamed treatment liquid is applied on a recording material before or after the image formation operation.
With respect to the treatment liquid applicator for use in such image forming apparatus, there is a proposal in that in order to maintain the level of a treatment liquid in a liquid container of the applicator, a ball valve is provided between the treatment liquid and the liquid supplying opening to control the level (i.e., volume) of the treatment liquid in the container by properly stopping supply of the liquid.
FIG. 11 is a schematic view illustrating a conventional applicator equipped with a treatment liquid supplying device. Referring to FIG. 1, an applicator 200 has a treatment liquid container 303, a tray 206 containing a treatment liquid 201 to be applied to a recording material, and a liquid flow path 302 connected with the container 303 and an upper portion of the tray 206 to feed the treatment liquid 201 from the container 303 to the tray 206. The end portion of the liquid flow path 302 facing the tray 206 has a venturi-type opening in which a liquid-level adjusting ball valve 301 having a hollow float is provided. The ball valve 301 is moved up and down depending on the level of the surface of the treatment liquid in the tray 206, and has a structure such that when the level of the surface of the treatment liquid reaches a predetermined highest level, the opening is closed, thereby stopping supply of the treatment liquid from the container 303 to the tray 206. In FIG. 11, reference numeral 233 denotes a squeeze roller to pick up the treatment liquid 201.
FIG. 12 illustrates the applicator illustrated in FIG. 11, which is inclined. In this case, a left side edge of the squeeze roller 233 in the axis direction thereof is not contacted with the treatment liquid 201 while a right side edge of the squeeze roller is contacted with the treatment liquid, thereby causing an insufficient liquid supply problem in that the treatment liquid 201 is not applied on the left side of a recording material.
FIG. 13 illustrates the applicator illustrated in FIG. 11, which is inclined but is in another state different from the state of the applicator illustrated in FIG. 12. Specifically, in FIG. 13, since the ball valve 301 has an open state because the level of the surface of the treatment liquid 201 is low, the treatment liquid is supplied to the tray 206 from the container 302. In this case, since the applicator 200 (i.e., the tray 206) is inclined, an overflow problem in that the treatment liquid 201 overflows from the right side wall of the tray 206 as illustrated by an arrow in FIG. 13 occurs.
For these reasons, the inventors recognized that there is a need for an image forming apparatus which has a treatment liquid applicator and which can satisfactorily apply a treatment liquid on a recording material without causing the insufficient liquid supply problem and the overflow problem mentioned above.